1. Field of the Invention
The present invention relates to an inkjet printer head, a nozzle plate of an inkjet printer head and a method of manufacturing a nozzle plate of an inkiest printer head.
2. Description of the Related Art
An actuator having a plurality of ink chambers in the inside and a piezoelectric element mounted on each of the ink chambers is used as an actuator of a head installed in an inkjet printer. In such an actuator, expansion and reduction of the volume of each ink chamber by the piezoelectric element applies pressure to ink in the ink chamber, and therefore, the ink is ejected to the external through an nozzle passage connected with the ink chamber.
This kind of actuator is typically constructed of a cavity plate and a nozzle plate. The cavity plate has ink chambers and ink channels to supply ink to the ink chambers. The nozzle plate has very small nozzle passages. Namely, the diameter of each nozzle passage is very small.
As the cavity plate is a member that is attached to a piezoelectric element through a diaphragm, it is necessary for the cavity plate to have a predetermined stiffness and a sufficient thickness. Furthermore, it is required that cavities each having a relatively large volume, which serves as ink chambers, ink channels, and so on, are formed in the cavity plate.
Accordingly, in fabrication of the cavity plate, it is difficult to form nozzle passages each having very small diameter on the cavity plate, together with the cavities having a relatively large stiffness and a relatively large thickness.
Therefore, the actuator has a thin nozzle plate that is a member independent of the cavity plate, and the nozzle passages are formed on the nozzle plate. Thus, it is possible to make the diameter of the nozzle passage very small. Furthermore, one end part of the ink ejection surface side of the nozzle portion, hereinafter referred to as straight conduit portion, can be shaped into straight. Accordingly, it is possible to enhance a performance to eject ink straight in the ejecting direction.
However, each of the cavity plate and the nozzle plate is a member formed by injection-molding ceramic, such as alumina, and thereafter sintering it. For this reason, in fabrication of the cavity plate and the nozzle plate by the injection molding, there is a case that burrs or flashes are formed and some nozzle passages are closed due to no good molding.
Therefore, after fabrication of the cavity plate and the nozzle plate by the injection molding, the ink ejection surface of the nozzle plate is ground in a grinding process in order to remove burrs or flashes and in order to form the nozzle passage each having a correct diameter and keep a predetermined setting length of each straight conduit portions.
However, the diameter of the nozzle passage is very small, and the length of the straight conduit portion is very short. For these reasons, there is no method of measuring the diameter of the nozzle passage and the length of the straight conduit portion, so that it is impossible to determine whether or not the diameter or the length is accurately equal to a predetermined setting value. As a result, there is a case that dispersion of the diameter or the length for each nozzle occurs.